The present invention relates to sensor systems for detecting the locked or unlocked condition primarily for openings such as doors for homes and buildings.
It is well established to provide means to detect the locked or unlocked condition of a door and to transmit a signal indicative of this condition to a central or local alarm or surveillance system. With doors such sensing is commonly done by detection of the position of a dead bolt. Many conventional locks for doors, however, do not utilize dead bolts for locking but instead provide locking by an internal lock of the door latch bolt or door knob. In the present invention a simple system is provided in which a signal is generated upon actuation of the lock for the latch bolt. At the same time, however, detection apparatus is provided in the door jamb in the door frame such that the locked condition is sensed only when the door is closed and the latch bolt is located in the door jamb. Now the signal can be readily transmitted to a central alarm or surveillance system or a local display whereby an indication will be provided of the locked or unlocked condition of the latch bolt and hence of the door when the latch bolt is engaged in the door jamb.
The apparatus of the present invention being of a relatively simple construction can be made to readily replace existing door latch assemblies as a retrofit. In addition it can be applied to some existing door latch assembly designs.
In one form of the present invention, the signal generating and detecting apparatus utilizes a permanent magnet which is pivotally mounted in a door latch assembly within the door. Upon actuation of the lock for the latch bolt the magnet is pivoted into alignment with a magnetic circuit that extends through the latch bolt. A detector, such as a reed switch, is located in that part of the magnetic circuit in the door jamb and will sense the presence and locked condition of the latch bolt when the magnetic field is energized by the pivotal location of the magnet into the magnetic circuit in response to actuation of the lock.
In a preferred form of the invention, magnetic signal generating detection apparatus is used in a compact construction readily adaptable for a conventional door latch assembly. However, as will be seen other forms of non-contact signal generating and detecting apparatus may be used.
Thus it is an object of the present invention to provide a contactless detection system for a door latch assembly for detecting and providing a signal upon closure of a door and placing the latch bolt in a locked condition.
It is another object of the present invention to provide a contactless detection system utilizing a magnetically actuated circuit for detecting and providing a signal upon closure of a door and placing the latch bolt in a locked condition.
It is still another object of the present invention to provide a contactless detection system adaptable for use with door latch assembly designs of generally conventional constructions and for detecting and providing a signal upon closure of a door and placing the latch bolt in a locked condition.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.